Hey gang,
I just had a brake job done by reputable people, and we are stumped.
Work done includes:

• New rotors (slotted Stoptechs front, drilled + slotted Stoptechs rear)
• New pads (Hawk HPS all around)
• New stainless brake lines (stop tech)
• Motul 600 brake fluid
• They bled the brakes properly

Problem: It feels soft/long travel. Almost like the booster is doing too good a job. The pedal doesn't really engage until an inch in, and it stops well and good but isn't as tight and responsive as I was expecting. It tightens right up if I pump the brakes, and I'd like the brakes to always engage as upfront as that.

Question:what's my problem? I have a NB Miata I track/autox, and it has a tight/immediate/upfront brake pedal feel that is easier to work with, ideally would get more like that. Is this a normal OEM feel?

Other notes:

• No visible fluid leak
• Master/slave seem to work fine
• ABS works as intended
  • No leaks visible there either
• brake pedal feel doesn't change as car heats up, or at least not noticeably (I think we are air-bubble free?)

Cheers!

 

3 things....

1. they didnt bleed the brakes properly. with the car off, pump the pedal. by the 3rd pump it should be a rock

2. keep driving and it will fix itself. something ive noticed after doing full fluid flushes is that it takes a couple days for the brakes to feel normal again. no idea why this is

3. try adjusting the rod on the back of the brake pedal that goes to the booster.

bonus thing..... the new fluid destroyed your master. depending how nasty the brake fluid was to begin with, you can destroy the hydraulics by pushing all that dirty fluid through it with the clean behind it.

what brake bleed technique are they using

 

@cr-rex cheers mate. From your comments:
1- It's a rock on pump 3.
2- I'll give it a shot to drive more and see if it self-corrects
3- Failing that, I'll futz with the pedal adjuster
4- Awesome! I think its an original master cylinder... so perhaps 30 years of living wore it out. The old fluid didn't look nasty but maybe it was sneaky bad
I don't know their technique beyond two dudes, one plastic bottle and vacuum hose. No special kit like this on amazon

Cheers!

 

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Point 2 is usually pads not being bedded in yet.

Resist the urge to pump the pedal fast when bleeding brakes as it can damage the master. I usually just use the mityvac and it works first time every time on the fd.

 

I've had this problem as well but haven't had a chance to work on the car to confirm, issue being that the first application of the brakes results in a lengthy pedal stroke but gets better upon second and third pump.

The last time I drove the car the ABS system went off while stopped on a steep downhill slope and turned off when returned to a regular flat surface.
I belive there is an air bubble in the system, possibly in the ABS pump that is causing the symptoms in my case and possibly yours also.

I would jack the rear of the car as high as you possibly can safely (and with out damaging the front bumper) and bleed the brakes with the ignition on. This should in theory force any trapped air to the highest point in the system and allow it to be bled out via rear calipers.

Sorry for the lengthy post.

 

I had a similar issue with my Miata after changing pads to the Hawk HPS. I only replaced pads, no brake fluid bleeding or any other work. After going on the street and bedding them in exactly how they recommend, the brakes would work, but the point at which the brakes really stopped the car was moved back, accompanied by a slightly spongy type of feel. After a month or two of driving the brakes have a good initial bite now at the start of hitting the brake pedal. If you are certain there is no trapped air in the system I would give them a little time.

 

^ My first thought was pads as well. None of the aftermarket pads I have used have had the initial bite of OEM pads.

 

It's also possible the pads aren't able to freely move and are binding up. The pins the pads slide on should be smooth and clean with a smear of grease on them.

If you have bad wheel bearings on the front you can get pad knock back - basically, the caliper squeezes the pads tight to the rotor to stop. Then you drive around and the wheel bearing has a wobble to it, which makes the rotor wobble and hit the pads a bit, slightly pushing the pads back into the caliper. This makes for more room between the pad and the rotor that has to be overcome when you hit the brakes. This typically shows up as the first hit of the brakes *while driving* is soggy, then if you immediately let off and hit the pedal again it's firmer, then another hit might be firmer still. Then drive for a few miles, hit the brakes, and it's back to sloppy. This happens more frequently on track cars that are pulling major G's in corners and really loading the wheel bearings.

Also just getting all the air out of the system is REALLY hard. Speed bleeders help a lot, and a vacuum or pressure bleeder can help a lot.

Dale

 

Most likely there is still air in the brake system. Especially in the ABS controller.
If the master cylinder is properly bleed, you might first have to bleed air from the pipes from the master cylinder where they go into the unit.
Then all outgoing pipes.
Then lastly at the calipers.

Never ever has this problem since June 1992. Not even when I replace all brakes with the Racing Brake system.

Proper procedures are is the answer.